The venous vasculature of the lower extremities includes superficial veins (such as the lesser and greater saphenous veins and their tributaries), deep veins (such as the anterior tibial, posterior tibial, peroneal, popliteal, deep femoral, superficial femoral, and iliac veins) and perforator veins (veins which connect the superficial veins to the deep veins). All veins of the lower extremities have valves which prevent the blood from falling (refluxing) back down the leg and help to keep the venous return blood flowing only in one direction, i.e., toward the heart. Each venous valve consists of two leaflets that move apart from one another as blood flows up the leg toward the heart and, thereafter, move toward one another so that they come into contact (i.e., coaptation) with each other, thereby preventing blood from backflowing in a direction away from the heart.
The congenital absence or incompetence of the venous valves results in a condition known as Chronic Venous Insufficiency (CVI). In CVI, venous blood tends to pool in the lower leg. This can cause distention of the veins (i.e., varicose veins), edema or swelling, pain, skin discoloration and, in severe cases, skin ulcers. In cases where the incompetent valves are located in superficial or perforator veins, the problem can be remedied by surgical removal of the affected veins. However, when the incompetent venous valves are located in deep veins, other treatment approaches must be considered because the deep veins are generally essential and cannot be removed.
The prior art has included various means for treating CVI, ranging from palliative techniques such as the wearing of contrictive stockings to surgical procedures such as vein removal, vein bypass, valvuloplasty or replacement of the affected venous valve with a transplanted homograft valve from elsewhere in the patient's venous vasculature or with a prosthetic valve. Examples of devices and techniques for treatment of incompetent venous valves are described in U.S. Pat. Nos. 7,018,408, 6,958,076, 6,902,576, 6,716,241, 6,652,578, 6,562,068, 6,458,153, 6,319,281, 6,299,637, 6,241,763 and 5,824,061 and United States Patent Application Publications Nos. 20070265699, 20070129788, 20070112423, 20070067021, 20070050013, 20060282157, 20060247762, 20060178730, 20060178729, 20060167543, 20050137681, 20050137676, 20040215339, 20040193253, 20040106976, 20040024447, 20030171802, 20030130727, 20040133267, 20030055492, 20030023300, 20020177894, 20010021872 and 20010011189.
In particular, United States Patent Application Publication No. 20040133267 (Lane) describes external stents to render incompetent venous valves competent. In one embodiment, the external stent comprises an inelastic bio-compatible cuff that encircles the venous valve cusps decreasing the internal diameter of the vein wall to allow apposition of the cusps and create improved competence of the valve.
There remains a need in the art for the development of new devices and methods for repairing incompetent venous valves.